Process and apparatus for cracking oils



Dec. 18, 1934. Wv F, MOORE 1,985,053

PROCESS AND APPARATUS FOR CRACKING OILS Filed Apr-11 18, 1928 CHA @6E llinlllllhl C ONDENSER 0R STRAGE Patented ec. 18, 1934 UNITED lsTA'lEs 1,985,053 l PROCESS AND Arriggtus FOR CRACKING William F. Moore, kJackson Heights, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application April 18, 1928, Serial No.` 270,817 11 claims. (c1. 19e-co) This invention. relates primarily to anv improved method, and suitable apparatus for carrying out the method, of converting higher boiling oils into lower boiling oils, particularly of the gasoline series. Itis a special object of the invention to provide a system of' the general character indicated for producing a blended product which is high in. its anti-knock characteristics. Various experiments have shown that the cracking of oils in the vapor phase, particularly under certain special conditions, will .result in the formation of lighter oils which are relatively high in their anti-knock qualities. This 'is commonly explained asV due to the presence of a larger percentagethan usual of unsaturated hydrocarbons in the final product. With this in view, the present invention contemplates a combined liquid and vapor phase system in which a portion of the nal product, which is formed by the blending of `two separate constituents produced by the system, results from purely liquid phase conversion while another,` portion of the final mixture results from purely vapor phase conversion. In the course of the process, certain of the heavier components from the vapor phase;; sy stem will be returned vto the liquid phase and may be carried into thejnal product of this phase. Byblending the products resulting lfrom the two distinct phases ofgthe process, a gasoline having the desiredhigh antiknock qualities is obtained. ,i

The invention is particularly `applicable to a system of the type commonly termed coil and drum or tube and tank, although itmay readily be applied to other cracking systems `as Well. Under one specific mode of application ofthe invention, it is proposed to` pass a; stream of oil througha heatingcoil under considerablepressure and then tointroduce the oilinto Aa drum or series of drums, or any equivalent enlarged zone, Where cracking of the oil may take place in the liquid phase or inthe combined liquid and vapor phase, if desired. Vapors which are generated or released within thedrums, or any connected expansion chamber, are then ledinto a fractionating tower; or other dephlegmator, from which the lighter ends emerge as vapors and are collected as a portion of the final product. The bottoms, or jcondensates, collected in the base of the dephlegmator. are'then, in accordance with the invention, passed into a zoneof reduced pressure where'a large portion of these condensatesare again yvaporized.V Vapors so formed may,"if desired, be subjected to further fractionationor recticationzto eliminate improperly condensed gasoline constituents and the remainder of this fraction may 'then be passed into a zone, which may be inthe form of a heating coil, where the oil is revaporized and cracking takes place in the vapor phase. Preferably, however, the entire mass of vapors will be passed directly to the coil in the vapor phase zone.' From this zone the products are then directed into another fractionating tower, or other dephlegmator, from the top` ofk which the lighter gasoline fraction is taken off, condensed, and collected. The condensates which collect in the base of this dephlegmator, on the other hand,will preferably be combined with the unvaporized portions which collect aty the lpoint where pressure `is released and this mixture is returned to any suitable point in the liquidphase cracking system. y

To obtain the desired'characteristics hereinbefore mentioned, it is contemplated mixing the products resulting from and separately taken off from the liquid phase and vapor phase treatments ofthe oil.

.Manywobjects and advantages, in addition to those already.mentioned,wil1 become apparent from .the detailed description of one admirable form of the invention, which will now begiven in conjunction withthe accompanying drawing,

which formsV a part hereof.

. of oil is admitted to thev system through a line 10 and is passed'by `means of thisline to an upperr section 11 of a heating coil located in a furnace 12. `This section vof the coil is preferably located in the upp'eror cooler portion of the furnace or maybe in a separate furnace or enclosure adapted to receive the heated gases generated'by the .burners 'employed in the furnace-12. For. convenience, this section ofthe coil may be designated the economizer. From the outlet end of the economizer, the charge is passed into a lower sectionof the heating coil, which may, `for convenience, be termed the preheatert section and which is preferably located in a hotter portion of the `furnace where it may receive radiant heat, as well as the heat of convection, ofthe flue gases. A transfer line 14 is provided for the purpose of introducing the heated charge, which has been raised to a cracking temperaturev in the lower section of the coil, into one or moreof. aseries of drumslor stills 15. If desired, only a single drum need be provided but it is preferable to employ a series of three or four drums,-which are interconnected by lines 16 above the liquid level and lines 17 below the liquid level in the several drums. These drums may be heated from an external source, if desired, or they maybe merely heat insulated.

From the lastof theseries of drums a vapor line 18 is' adaptedl to convey the generated lighter vapors to a suitable dephlegrnatoror ractionating tower 19, which may, for example, be of bubble tower construction, if desired.

In this tower a separation between the lighter and heavier constituents of the vaporsfwill be eiected and the lighter constituents will ,pass out of the top of the tower through a suitable refiuxing condenser 2G from which the vapors of desired endpoint pass on Ythrough aline 21- to a nal condenser 22 and a collection lrecep-v tacle 23. The heavier constituents of the vapors entering the tower 19 are. drawn oil` `from the latter by means of a transfer linen24 and are passed through a reducing valve into a vaporizer drum or expansion chamber 25. Here the greater portion of the condensate withdrawn from the base of the tower 19 will vbe .vaporized under the reduced pressure and will be passed 4through a line 26 to a separate heating coil 27prefer ably located inthe same furnace with the economis/er section and preheater section of ,the coil of the liquid phase system. If desired,:the coil 27 could be locatedina separatefurnace, although it is deemed` preferable to place itin the same furnace12ata point just abovethe preheater section Wherethe relatively hot gases circulate around its tubesbut Vwhere no direct flame orradiant Aheat ispresent. n In ,the line'26, suitable means, such as fractionator26, may be provided, if desired, for the purpose of fractionating or rectifying the vapors so-as to eliminate any oi the gasoline fractionwhich should have gone over through the condenser :but which was knocked back together -withheavier components. -If this is done, however, itxwill be necessary to apply additional heat inthe coil 27 to revaporize the. oil. Reference numerals 42, 43, and 44, indicatevalves ywhereby fractionator 26 may be rendered activeer inactive.

rReiluXing liquid may be supplied tofthefractionator in the usual manner through line 48. When the fractionator is. inguse gasoline fractions pass off from the topthereof through ,line 45 for any desired treatment, valve 46S-serving to maintain the desiredv pressure .f in vtliefractionator, lwhile the condensate collectingain the base of the fractionatorpasses through line 47 to coil 27. When the fractionator'is `not in use the vaporized gasoline fractionsarepassed from the vaporizer 25.through co'il 27 wherein they are subjected to .cracking in the 'vapor phase.

From the outlet end of the coi1'27 wherein. the vapors have been subjected Ato Afurther cracking in the vapor phase, a line 28 serves to conveythe vapors to a suitable dephlegmator or fractionating tower 29. Here the lighter lvapors pass on through and are carried out at the topthrough a reiiuxing condenser 30 and onto a `iinal condenser 31 and collection receptacle. 32. The heavier constituentsv of the vapors introduced into the dephlegmator 29 will -preferablyfbe withdrawn through aline 33 at the base of the tower-and passed to a suitable surge pump 34. In a similar manner, the heavier.. constituentsk of l the; condensate withdrawn. from'ithe dephlegmator 19, and which are not vapori'zed' in the drum I in the` drawing.this is preferably. effected at al pointinlthe preheater section 13 off-,fthe heating coil where the temperature of the recycled material will be substantially the same as that of the fresh charge which has been passed through the economizericoil.. Obviously, if desired, the recycled stock may be introduced at any other suitablevrpoint in the yliquid phase system. In

lieu of a .single surge pump 34, it may be found fpreferableto employ two separate pumps for returning the material withdrawn from the base of the drum and that withdrawn from the base of the dephlegmator 29. A slight difference in pressure will probably be found to exist at thesesponts due .chiefly .tozthe friction encounteredin the ,passagebf the vaporsf throughthe 0011.27. .Furthermora .the system may beso operated,1if,.desired, .as to provide .a further drop in pressure between Jthe coil. 2'7 `and the dephlegmator 29.

Suitable tardrawing lines 37 will, of course, be provided in connectionwith the drums 15 for passing the heavierV residual oil .collecting in these drums yto suitable storage. In the line 10,

a .valve 38.1'nay be provided, if desired, .to force the fresh charge through a line 39, a heat exchange coil 40, and a return line 41. Inthis way the fresh charge Vmay have its temperature raised toa .certainextentbefore `it is introduced into the economizer .coil and-suitable means is provided Vforregulating thehtemperaturc at the top of the tower 19. Obviously, the valve 38 may either .be .completely open, .partially open, .or completelyaclosed, .to suit the particular conditions.' Reference 'numeral'23 indicates a pipe having` control .valve 32', by which distillate in theireceptaclesllZS and 32. may-be blended if desired; @In thegopera'tion of the system, the temperature and pressure conditions adapted may vary withinvwide limits. It :is contemplated-as preferable kto operate theiliquid-pha-se portion-of the system at laf substantially uniformv vpressure throughoutfalthough Ait is fclearlyyvithinthe scope ofthe present invention to `provide a drop in pressureleither4 between the heating coiland the'drums or 'stillsl `15, or'between the latter and thef-dephlegmatori19 or at-both points. Under anyof these'modesiof operationfthe' coils 11 and 13 will preferably carry Vthe charge under a pressure oibetween 100l pounds and 500 pounds,--or evenA higherfiffdesired. `In the vaporizing drum l25v it is contemplated 'that a pressure only slightly-abovey atmospheric, or possibly up to or slightly Vabove-'100 pounds, will be carried and' this pressure-will preferably be maintained throughout thevapor'phase portion of 'the system, except -for'minor drops due tofriction. Suitable temperatures will be carried-in the various sections ofv thesyst'em-to effect cracking primarily inthe' drums 15fandfthe coil 2'7, although some crackingmay also take place in thecoil "13.

`lv`While .oneisadmirable mode of practicing'the' n inventionhas been disclosed in detail, it will be understood .that 'it fiscapable of various modications without-departing vfrom' thel spirit or;

What I claim is:

1. A process for the conversion of higher boiling oils into lower boiling oils which comprises heating a body of oil under such conditions of temperature and pressure as to effect cracking in the liquid phase, fractionating the generated vapors, releasing the pressure on the reflux condensates resulting from said fractionation to effect separation of vapors from liquid constituents, passing the vapors thus separated through a vapor phase cracking zone, fractionating the products from this zone, and returning to the cracking portion of the liquid phase system the unvaporized portions of the condensates from the first mentioned fractionation after the release of pressure.

2. A process for the conversion of higher boiling oils into lower boiling oils which comprises heating a body of oil under such conditions of temperature and pressure as to effect cracking in the liquid phase, fractionating the generated vapors, releasing the pressure on the refluxed condensates resulting from said fractionation to effect separation of vapors from liquid constituents, passing the vapors thus separated through a vapor phase cracking zone, fractionating the products from this zone and returning to the cracking portion of the liquid phase system the unvaporized portions of the condensates from the first mentioned fractionation after the release of pressure, as well as the refluxed condensates resulting from the second mentioned fractionation.

3. In apparatus of the class described a heating coil, means for applying heat thereto, a

` 'drum adapted to receive a body of oil, means for forcing a stream of oil through said coil and into said drum, a dephlegmator for condensing a portion of the vapors generated in said rdrum, a vaporizer adapted to receive the condensate formed in said dephlegmator, means between said dephlegmator and vaporizer for reducing the pressure on said oil, a second heating coil adapted to receivethe vapors from said vaporizer, means for fractionating the products from the last mentioned coil, and means for returning the unvaporized portions from said vaporizer to said first mentioned coil. q

4. In apparatus of the class described a heating coil, means for applying heatthereto, a drum adapted to receive a body of oil, means for forcing a stream of voil through said coil and into said drum, a dephlegmator for condensing a portion of the vaporsgenerated in said drum, a vaporizer adapted to' receive the condensate formed in said dephlegmator, a heating coily adapted to receive the vapors from said vaporizer, means for fractionating the products from the last mentioned coil, and means for returning the unvaporized portions` from said vaporizer and the condensate formed in said fractionating means to said rst mentioned coil.

5. A process for the conversion of higher boiling hydrocarbon oils into lower boiling oils which comprises heating oil under such condi-` tions of temperature and pressure as to effect cracking thereof', separating the resulting cracked products into vapors and a liquid residue, fractionating the vapors into light overhead fractions, higher boiling range fractions and intermediate boiling range fractions, re-

turning higher boiling range fractions so obtained to the oil undergoing heating and cracking, heating intermediate boiling range fractions so obtained to a vapor phase cracking temperature to form high anti-knock gasoline fractions, separately fractionating the vaporous products of the last mentioned cracking operation to separate as reflux condensate fractions heavier than the final desired product, separately returning reflux condensate so formed to said oil undergoing heating and cracking for further cracking and condensing the vapors remaining uncondensed after fractionation.

6. A process in accordance with claim 5 wherein the final desired product is formed by blending said light overhead fractions with the condensate formed by condensing said vapors last mentioned.

7. A process according to claim 5 wherein said light overhead fractions fall mainly in the gasoline boiling range and wherein said intermediate boiling range fractions comprise some gasoline constituents. f

8. A process according to claim 5 wherein said light overhead fractions fall mainly in the gasoline boiling range and wherein said intermediate boiling range fractions are free from gasoline constituents.

9. A process for the conversion of higher boiling hydrocarbon. oils into lower f boiling oils which comprises heating oil under such conditions of temperature and pressure as to effect cracking thereof, separating the resulting cracked products into vapors and a liquid residue, fractionating the vapors into light overhead fractions, higher boiling range fractions and intermediate boiling range fractions, returning higher boiling range fractions so obtained to the oil undergoing heating and cracking, heating intermediate boiling range fractions so obtained to a vapor phase cracking temperature to form high anti-knock gasoline fractions, separately fractionating the vaporous products of the last mentioned cracking operation to separate as reflux condensate fractions heavier than the yfinal desired product, condensing the vapors remaining uncondensed after fractionation and blending said light overhead fractions with the condensate formedby condensing said vapors last mentioned, to form a final desired product.

10. A process according to claim 9 wherein said light overhead fractions fall mainly in the gasoline boiling range and wherein said intermediate boiling range fractions comprise some gasoline constituents. i

1l. A process according to claim 9 wherein said light overhead fractions fall mainly in the gasoline boiling range and wherein said intermediate boiling range fractions are free from gasoline constituents.

WILLIAM F. MOORE. 

